No credit card required
Browse credit cards from a variety of issuers to see if there's a better card for you.
The AAoA isn't considered when underwriting, although a lot of brand new accounts can make an underwriter a little uneasy since there isn't a long track record of you being able to manage that much credit.
If the paid medical collection from 2012 is your only negative & you have a 642 credit score then I don't see your credit having much of an issue qualifying for USDA.